It may be exhausting, but I'd start looking through the movement serial numbers of every single watch which interests you, rather than searching for "1958". Perhaps you've been doing this already. That's 16M-ish as you know.
Freddo kindly pointed me in that direction with a chart with the codes for each year so it's what I'll be starting to do from now.
@ricky2slicky started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
It may be exhausting, but I'd start looking through the movement serial numbers of every single watch which interests you, rather than searching for "1958". Perhaps you've been doing this already. That's 16M-ish as you know.